Control system



June 24, 1930. J. H. BELL CONTROL SYSTEM Filed April 10, 192

, n/ P W H. m N\ & 7 Q T 73 m QR q m l v, QR Mn ,0 ELI] nj "A R \w \v 1 & w\ R. wh J MW w M n O nu .i \w a Q .R\ 4. (\JWN... N |||l {Nil N w w ww QM Q vicesr Patented. June 24, 1930 UNITED STATES JOHN H. BELL, OF SOUTH ORANGE, NEW

JERSEY, ASSI GNOB TO BELL TELETHONE LABORATORIES, INCORPORATED, OF NEW YORK, N. Y., A OORLORATION OF NEW YORK CONTROL SYSTEM Application filed April 10,

This invention relates to control systems, and more particularly to systems for synchronizing the movement of controlled de- The radio broadcasting art has now developed to the sta e that signals picked up at a studio or pic -u station may be supplied overa networ of wire lines to a arge number of radio stations, at which the signals are caused to modulate high :Ere uency carrier waves to be broadcast. It has een found necessary, in connection with broadcasting systems involving the transmission of signals, such as speech or music, over wire lines from apick-up point to one or more broadcasting transmitters, to provide control means adapted to adjust the volume o g ends of the line. The necessity for this is uite generally known to arise from the fact 1: atv the wire lines and associated amplifiers and repeaters have a limited volume capacity, and the signal volume at times may relator have the same characteristics as the original signal. The volume control devices at the respective stations are enerally operated in accordance with e ectric impulses transmitted over control lines separate from the signal lines. The control lines may include mechanical relays or repeaters requiring a considerable time for operation, and hence the control impulses may be delayed more or less depending upon the number of repeaters and the length of the lines. For this reason the control impulses may reach the several controlled stations at difi'erent instants.

The signals, however, because repeated by space discharge devices, are ordinarily propagated without material delay. As a result the delay of the control impulses may als at the transmitting and receiving.

1926. Serial No. 101,031.

at the broadcasting station. The control impulses will not ordinarily immediately effeet a compensating reduction in the signal 'volume "supplied to the broadcasting trans- -mitter, hence a volume peak, not actually characteristic of the original si nal is produced in the broadcast wave. 11 the present invention, means is provided to delay the volume control action at the pick-up vstation sufficiently to enable a compensating action to be effected at the broadcasting station at the proper instant, namely at the instant that the signal volume change would otherwise become efi'ective at the latter station.

It is an object of this invention to adjust the time of propagation of impulses from a source over paths normally of different electrical length.

A speclfic object is to synchronize the operation of a plurality of devices controlled from a single station.

A more specific object is to compensate for the diflerences in the time of transmission of control impulses over different paths from a source to distant control devices, so that any desired time interval between the operation of these devices may be secured.

A related object is to adjust theinterval between a plurality of control actions, effective at separate points with respect to a signal wave, to the time of propagation of the wave between the respective oints.

The invention provides, as a eature, a control system including controlled and controlling devices and interconnecting lines, With-suitable delay circuits-or elements for eflecpting the several objects above enumerate j The invention broadly may be explained I as a controlsystem, wherein electromagnetic is connected to the primer lines to a common control device, by means of which, impulses are supplied to the lines for operating the controlled devices. The impulses may be similar to telegraph impulses and may be relayed, and repeated by telegraph or similar relays. Such relays, however, have a timedelay in operation, so that impulses supplied to one controlled device may be delayed more or less than those supplied to another device at a difierent location, depending upon the number of relays included in the respective control paths.

, Other factors also mayafiect the time of propagation of the control impulses from the control station to the different controlled devices. To enable the action of the controlled devices to be effective at the proper instants, at the several desired points, this invention rovides delay circuits to enable the time oi propagation of control impulses to the several controlled devices to be adjusted. As a result, the interval between the control actions may be suitably adjusted.

The invention may be applied, in practice, to a volume control system, wherein it is desired to adjust the interval between signal volume adjustments made respectively at a pickup stationand at one or several broadcasting stations to the time required for the propagation of a signal volume change between these stations. 4

The invention is illustrated in the figure of the drawings in connection with a volume control circuit associated with a chain of radio broadcasting stations.

Referring to the drawings, the ,system therein shown comprises a pick-up station 10 and a plurality of radio broadcasting stations 11 and 12. The pick-up station and the several broadcasting stations are provided with volume control devices13, 14 and 15, respectively, which are connected by a wire network to a control station 16. The wire network has included,in the individual branches extending tothe. controlled devices 13, 14 and 15, the delay circuits 17, 18 and 19, respectively.-

Atthe station 10 a pick-up transmitter 20 winding of a si a1 transformer 21, in series with a source 0 current represented as a battery 22.- The secondary winding of the transformer is connected to a volume control potentiometer comprising a resistance 23 and a control arm 38, which is in turn connected to the input terminals of an amplifier 24. This am lifier may be any one of many well-known orms,

but preferably includes space discharge tubes. The output terminals of this amplifier are connected to a wire line 25, which includes a repeater station 26, at which there may be provided s ace dischar e amplifiers and re eaters -o any desire type,

referab y emp oying s ace discharge tubes.

he output terminals 0 the repeater station 'eral tele messes 26 are connected to a second wire line 27 which extends to a control potentiometer comprising a resistance 28 and a control arm 38, at the broadcasting station 11. This potentiometer is connected to a suitable space discharge amplifier 29, which is adapted to supply'amplified signal waves to the radio transmitter 30, connected to the antenna 31.

The transmission line 27 has connected to it a branch 32 extending through a second repeater station 26 to a control potentiometer, including a resistance 33 and a control arm 38, at the other'broadcasting station 12; this station also including an amplifier 29 and a radio transmitter 30 associated with an antenna 31-. The transmitting apparatus at station 12 may be identical with the corresponding apparatus at sta tion 11.

The control arms38, of the potentiometers at the respective stations, are adapted to be adjusted by driving means 13, 14 and 15, which may be of any desired type. The potentiometers 23-38, 28-38 and 33-38 constitute the controlled devices hereinbe-. fore and heinafter mentioned. The driving means includes solenoids 34 and 35 having an armature 36 connected to a gear 37, which is adapted to operate the arms 38. The respective solenoids may have one terminal connected to ground and the opposite terminal connected to one side. of the control line 39, which may include the sevaphrepeater stations 40. The line 39 a so includes, at the several stations 10, 11 and 12, delay circuits 17, 18 and 19 respectively which may be any one of vari- 'ous forms, but which are illustrated as ineluding series inductance elements 41 and 5 shunt capacity elements 42.

The control. station. 16 includes keys 43 and 44, adapted to connect the batteries 45 and 46 between ground and the respective sides of the control line 39.

The system just described operates as follows: Sound waves such as speech ormusic are supplied to the pick-up transmitter 20 which roduces corresponding electrical waves t at are supplied through transformer 21 and the associatedpotentiometer 23-38 to :the amplifier 24. The volume of signals may be controlled by adjustment of the arm 38, which varies the voltage of the si al waves supplied to the input circuit 0 the amplifier 24. The signal waves fromamplifier 24 are supplied to the wire line 25 and are repeated at the repeating station 26 to the line 27, over which they are transmitted through the potentiometer 2838 and amplifier 29 to the radio broadcasting transmitter 30 at station 11. They are here caused to modulate radio frequency carrier waves and the resulting modulated waves a are supplied to the antenna 31.

Signal waves are also supplied over. the a line 32 in like manner to the radio trans-' mitter 30 which supplies similar modulated waves to the antenna 31 at station 12.

The volume of signals supplied to the line 25, the repeater station 26 and the lines 27 and 32 may be controlled by means of the keys 43, and 44 at the control point 16. When key 43 is depressed all of the solenoids 34 at the several stations 10, 11 and 12 are energized. Likewise, when the key 44 is depressed all of the solenoids 35 are energized.

Solenoids 34 cause a movement of their associated potentiometer arms 38 in one direction, whereas solenoids 35 cause a movement of these arms in an opposite direction. Thus, by energizing the solenoids 34'and 35, any desired movement of the switch arms38 relative to the resistances of potentiometers 23, 28 and 33 may be produced. I

When solenoid 35 at station 10 is energized the switch arm 38 is rotated to the left, and accordingly the amplitude level of the si al current supplied to lines 27 and 32 is increased. When the solenoids 35 at stations 11 and 12 are energized, they cause the switch arms 38, associated with resist-.

ances 28 and 33, respectively, to be rotated to the ri ht and hence produce a change in the amp itude le'velof the signal currents supplied to the radio transmitters, which change is equal and opposite to the increase in level caused by the adjustment of the potentiometer at stationlO. The amplitude levelof the signal current supplied to the lines 27 and 32 at station 10 is consequently increased, whereas the amplitude level of the signal current supplied to the radio transmitters at stations 11 and 12 is decreased to the same extent. On the other hand when the solenoids 34 are energized, the amplitude level of the signal current supplied to the lines from the station 10, is decreased, whereas the amplitude level of the signal currents supplied to the transmitters at the broadcasting stations is corresipondingly increased.

this method of control, the amplitude leve of the signal currents, supplied to the radio transmitters at the broadcasting stations 11 and 12, may be adjusted to have any desired relation to the amplitude level of the signal currents'supplied at the pick-up station 10. Cons uently, the volume of the signal, although 0 anged at station 10, may be restored at stations 11 and 12 to a value bearing a definite relation to that produced at the pick-up station, for example it ma be restored to the samevalue.

By virtue of the action of the delay networks 17, 18 and 19, the volume control adjustments at the several stations are efiected at desired predetermined intervals. The keys 43 and 44 will ordinarily be located at the same place as the pick-up transmitter and 40 respectively, as illustrated, the transmission of the control impulses to these stations will be considerably delayed. The impulses supplied to station 12 ,will ordinarily be delayed to a greater extent than those supplied to station 11, because ofv the greater-number of repeater stations included in this path, and the impulses supplied to both of these stations will in general be delayed to a greater extent than those supplied to the station 10.

The delay circuits 17, 18 and 19 are therefore designed to change the electrical length of the paths to the respective stations, so that the diflerence in time of propagation of the control impulses over the several paths is equal to the time of propagation of a signal volume change from the pick-up stag tion to the respective broadcasting stations.

As a result, control actions will be effective at the several broadcasting stations at the instant when a volume change produced by the potentiometer 2338 arrlves. Undesired volume peaks, which tend to introduce distortion in the broadcast signals, will accordingly be prevented.

Although this invention has been described in connection with a particular embodiment, it is susceptible of general application. For exam le, any, suitable dela circuits may be emp oyed, and the use 0 mechanical as well as electrical devices is contemplated. The devices shown in the drawtype. The volume control devices and the impulse sending devices ma b''modified, for example, to include a c ain of relays Likewise, the number of broadcasting stations may be almost indefinitely increased,

and the signal and control networks corre-' spondingly extended. It is also evident that any one o the delay circuits may be omitted, the other delay circuits being designed so that the control impulses are eifective at all stations at the proper instant.

The invention is therefore to be limited only' as indicated by the scope of the apings merely serve to illustrate a convenient m connecting said adjustable devices with said control station, over which impulses are transmitted, for varying the adjustment of said devices, and means included in said circuits. for delaying the transmission of said impulses over certain of said circuits,

-whereby the relative time of operation of said devices may be adjusted.

3. In a broadcasting system, a pick-up station, a plurality of broadcasting stations, means for'controlling the volume of signals at said pick-up station in one sense and at said broadcasting stations in an opposite sense, said means including elements inherently tending to delay the control operastations may be obtained.

tions at certain of said stations, and means for adjusting the delay, whereby control action'sat all of said stations may be effected in a predetermined time .order. v

4. The method of volume control of sig nals which comprises, simultaneously transmitting control impulses from the'common control station over paths requiring difli'erent intervals for the propagation of said impulses, and interposing delay in the propagation of impulses in certalnof said at s. p 5. In a broadcasting system including a pick-up station and a plurality of broadcasting stations and a control station, the method of volume control of signals which comprises, transmitting control impulses from the control station to the signal pickup and broadcasting stations, to vary the. volume of signals at said pick-up station in one sense and at said broacasting stations in an opposite sense, in accordance with said impulses, and adjusting the time or propa: gation of said impulsesto all of said stations, whereby a desired difference in time of effecting volume variations at the several 6. In a volume control system, a plurality 'of volume control devices at a plurality of separated stations, means for transmitting 1I I1p11lSeS, controlling all of said devices over circuits inherently requiring difi'erent interi vals for propagating said impulses, and

means in said circuits for adjusting said in- 'tervals.

7. In combination, a control station, a

plurality of devices to be controlled, a plurallty of paths having different time factors for the transmission of impulses connecting said control station and said devices, and

-means for substantially equalizing the time of propagation of said impulses over all of sald aths. i

8. n combination, a source of impulses, a

meaeea plurality of electromechanical devices, a wire line. connected to said source and ncluding separate branches connected to individual devices, and, included in said branches, delay circuits for equalizing the time of propagation of said impulses to all lay circuit associated with at least one ofsaid branches.

10. In a control system, the method 0 eflecting control of a plurality of devices which comprises, adjusting the interval between a plurality of control actions effective at separate points with respect to a signal wave, to the time of propagation of said wave between said respective points.

a In witness whereof, I hereunto subscribe my name this 5th day of April, A. D., 1926.

JOHN H. BELL. 

